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ijod.js
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ijod.js
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/*
*
* Copyright (C) 2011, The Locker Project
* All rights reserved.
*
* Please see the LICENSE file for more information.
*
*/
/*
* Indexed JSON On Disk
*/
var fs = require('fs');
var path = require('path');
var deepCompare = require('./deepCompare');
var sqlite = require('sqlite-fts');
var zlib = require("compress-buffer");
var lutil = require("lutil");
var async = require("async");
var mmh3 = require("murmurhash3");
function IJOD(arg) {
if(!arg || !arg.name) throw new Error("invalid args");
var self = this;
this.transactionItems = null;
self.name = arg.name;
self.gzname = arg.name + '.json.gz';
self.dbname = arg.name + '.db';
};
IJOD.prototype.open = function(callback) {
var self = this;
try {
self.fda = fs.openSync(self.gzname, 'a');
self.fdr = fs.openSync(self.gzname, 'r');
var stat = fs.fstatSync(self.fdr);
self.len = stat.size;
} catch(E) {
return callback(E);
}
self.db = new sqlite.Database();
self.db.open(self.dbname, function (err) {
if(err) return callback(err);
self.db.executeScript("CREATE TABLE IF NOT EXISTS ijod (id TEXT PRIMARY KEY, at INTEGER, len INTEGER, hash TEXT);",function (err) {
if(err) return callback(err);
callback(null, self);
});
});
};
IJOD.prototype.close = function(callback) {
if (this.closed) {
console.error("Double close in IJOD");
var E = new Error("double close");
console.log(E.stack);
return callback();
}
this.closed = true;
fs.closeSync(this.fda);
fs.closeSync(this.fdr);
this.db.close(callback);
}
exports.IJOD = IJOD;
IJOD.prototype.startAddTransaction = function(cbDone) {
if (this.transactionItems) return cbDone();
this.transactionItems = [];
this.db.execute("BEGIN TRANSACTION", function(error, rows) { cbDone(); });
};
IJOD.prototype.commitAddTransaction = function(cbDone) {
if (!this.transactionItems || this.transactionItems.length == 0) return cbDone();
//console.log("Commiting %d items", this.transactionItems.length);
var totalSize = this.transactionItems.reduce(function(prev, cur, idx, arr) { return prev + arr[idx].length; }, 0);
var writeBuffer = new Buffer(totalSize);
var idx = 0;
var self = this;
lutil.forEachSeries(self.transactionItems, function(item, cb) {
item.copy(writeBuffer, idx);
idx += item.length;
cb();
}, function(err) {
fs.write(self.fda, writeBuffer, 0, writeBuffer.length, null, function(err, written, buffer) {
// We end the transaction
writeBuffer = null;
self.transactionItems = null;
if (err) {
console.error("Error writing to IJOD: %e", err);
} else if (written != totalSize) {
console.error("Only %d written of %d bytes to IJOD", written, totalSize);
}
self.db.execute("COMMIT TRANSACTION", function(error, rows) { cbDone(); });
});
});
};
/// Abort a pending add transaction
/**
* Any pending write chunks are destroyed and the database transaction is rolled back.
* This is safe to call without a transaction started.
*/
IJOD.prototype.abortAddTransaction = function(cbDone) {
if (!this.transactionItems) return cbDone();
this.transactionItems = null;
this.db.execute("ROLLBACK TRANSACTION", function(error, rows) { cbDone(); });
};
// takes arg of at least an id and data, callback(err) when done
IJOD.prototype.addData = function(arg, callback) {
if(!arg || !arg.id) return callback("invalid arg");
arg.id = arg.id.toString(); // safety w/ numbers
var tmpJson = JSON.stringify(arg);
var hash = mmh3.murmur32HexSync(tmpJson);
if(!arg.at) arg.at = Date.now();
var self = this;
this.startAddTransaction(function() {
var tmpJson = JSON.stringify(arg);
var gzdata = zlib.compress(new Buffer(tmpJson+"\n"));
self.transactionItems.push(gzdata);
var at = self.len;
self.len += gzdata.length;
self.db.execute("REPLACE INTO ijod VALUES (?, ?, ?, ?)", [arg.id, at, self.len-at, hash], callback);
});
}
// adds a deleted record to the ijod and removes from index
IJOD.prototype.delData = function(arg, callback) {
if(!arg || !arg.id) return callback("invalid arg");
arg.id = arg.id.toString(); // safety w/ numbers
if(!arg.at) arg.at = Date.now();
arg.type = "delete";
var self = this;
var gzdata = zlib.compress(new Buffer(JSON.stringify(arg)+"\n"));
fs.write(self.fda, gzdata, 0, gzdata.length, null, function(err, written, buffer) {
if (err) {
return callback(err);
}
var at = self.len;
self.len += gzdata.length;
self.db.execute("DELETE FROM ijod WHERE id = ?", [arg.id], callback);
});
}
// this only calls callback(err, rawstring) once!
IJOD.prototype.getOne = function(arg, callback) {
if(!arg || !arg.id) return callback("invalid arg");
arg.id = arg.id.toString(); // safety w/ numbers
var self = this;
var did = false;
self.db.query("SELECT at,len FROM ijod WHERE id = ? LIMIT 1", [arg.id], function(err, row){
if(did) return; // only call callback ones
did = true;
if(err) return callback(err);
if(!row) return callback();
var buf = new Buffer(row.len);
fs.readSync(self.fdr, buf, 0, row.len, row.at);
var data = zlib.uncompress(buf);
return callback(err, arg.raw ? data : stripper(data));
});
}
// will call callback(err, rawstring) continuously until rawstring==undefined
IJOD.prototype.getAll = function(arg, callback) {
if(!arg) return callback("invalid arg");
var params = [];
var sql = "SELECT at,len FROM ijod ";
if(arg.limit)
{
sql += " LIMIT ?";
params.push(parseInt(arg.limit));
}
if(arg.offset)
{
sql += " OFFSET ?";
params.push(parseInt(arg.offset));
}
var self = this;
self.db.query(sql, params, function(err, row){
if(err) return callback(err);
if(!row) return callback();
var buf = new Buffer(row.len);
fs.readSync(self.fdr, buf, 0, row.len, row.at);
var data = zlib.uncompress(buf);
return callback(err, arg.raw ? data : stripper(data));
});
}
// takes a new object and checks first if it exists
// callback(err, new|same|update)
IJOD.prototype.smartAdd = function(arg, callback) {
if(!arg || !arg.id) return callback("invalid arg");
arg.id = arg.id.toString(); // safety w/ numbers
var self = this;
var start = Date.now();
self.getOne(arg, function(err, existing){
//console.log("getOne in %d", (Date.now() - start));
if(err) return callback(err);
// first check if it's new
if(!existing)
{
self.addData(arg, function(err){
if(err) return callback(err);
callback(null, "new");
});
return;
}
try { var obj = JSON.parse(existing); } catch(E){ return callback(E); }
delete obj.at; // make sure not to compare any timestamps
delete arg.at;
// they're identical, do nothing
if (deepCompare(arg, obj)) return callback(null, 'same');
// it's different, save an update
self.addData(arg, function(err){
if(err) return callback(err);
callback(null, "update");
})
});
}
IJOD.prototype.batchSmartAdd = function(entries, callback) {
//console.log("Batch smart add %d entries", entries.length);
var t = Date.now();
var self = this;
// TODO: We have 5 attempts to write and then we blow up, we need something smarter to do with this data
self.batchAttempt = self.batchAttempt || 0;
if (++self.batchAttempt > 5) {
self.batchAttempt = 0;
console.error("Out of attempts trying to batchSmartAdd, blowing up");
throw new Error("Unable to batchSmartAdd");
}
function handleError(msg) {
console.error("Batch smart add error: %s", msg);
self.abortAddTransaction(function() {
setTimeout(function() {
self.batchSmartAdd(entries, callback);
}, 500);
});
}
var script = ["CREATE TEMP TABLE IF NOT EXISTS batchSmartAdd (id TEXT)", "DELETE FROM batchSmartAdd", "BEGIN TRANSACTION"].join(";") + ";";
self.db.executeScript(script, function(error, rows) {
self.db.prepare("INSERT INTO batchSmartAdd VALUES (?)", function(error, stmt) {
if (error) return handleError(error);
async.forEachSeries(entries, function(entry, cb) {
if (!entry) return cb();
stmt.bind(1, entry.id, function(err) {
if (err) return cb(err);
stmt.step(function(error, row) {
if (error) return cb(error);
stmt.reset();
cb();
});
});
}, function(error) {
if (error) return handleError(error);
self.db.execute("COMMIT TRANSACTION", function(error, rows) {
if (error) return handleError(error);
stmt.finalize(function(error) {
self.db.execute("SELECT id,hash FROM ijod WHERE ijod.id IN (SELECT id FROM batchSmartAdd)", function(error, rows) {
if (error) return handleError(error);
var knownIds = {};
rows = rows || [];
rows.forEach(function(row) {
knownIds[row.id] = row.hash;
});
self.startAddTransaction(function() {
async.forEachSeries(entries, function(entry, cb) {
if (!entry) return cb();
if (knownIds[entry.id]) {
// See if we need to update
entry.id = entry.id.toString(); // safety w/ numbers
var hash = mmh3.murmur32HexSync(JSON.stringify(entry));
// If the id and hashes match it's the same!
if (hash == knownIds[entry.id]) {
return cb();
}
}
self.addData(entry, cb);
}, function(error) {
if (error) return handleError(error);
self.batchAttempt = 0;
self.commitAddTransaction(callback);
//console.log("Batch done: %d", (Date.now() - t));
});
})
});
});
});
});
});
});
};
// utilities to respond to a web request, shared between synclets and push
IJOD.prototype.reqCurrent = function(req, res)
{
var streaming = (req.query['stream'] == "true");
var options = {};
if(req.query['limit']) options.limit = parseInt(req.query['limit']);
if(req.query['offset']) options.offset = parseInt(req.query['offset']);
var ctype = streaming ? "application/jsonstream" : "application/json";
res.writeHead(200, {'content-type' : ctype});
var first = true;
this.getAll(options, function(err, item){
if(err) logger.error(err);
if(item == null)
{ // all done
if(!streaming) res.write("]");
return res.end()
}
if(streaming) return res.write(item+'\n');
if(first)
{
first = false;
return res.write('['+item);
}
res.write(','+item);
});
}
IJOD.prototype.reqID = function(req, res)
{
this.getOne({id:req.params.id}, function(err, item) {
if (err) logger.error(err);
if (!item) return res.send("not found",404);
res.writeHead(200, {'content-type' : 'application/json'});
res.end(item);
});
}
// make a string and return only the interior data object!
function stripper(buf)
{
var s = buf.toString("utf8");
return s.slice(s.indexOf('{',1),s.lastIndexOf('}',s.length-3)+1); // -3 accounts for }\n
}